DESCRIPTION: In this project the investigators propose to take advantage of recent advances from Center laboratories in the temporal and spatial regulation of transgene expression to address questions about the role of the medial temporal lobe system of mammals in the storage and retrieval processes of memory. Questions to be addressed include identification of the function of different medial temporal lobe regions in explicit memory, determining whether different sites are functionally similar or specialized. If subregions are specialized, how are they specialized and do they participate in different types of memory tasks--- spatial, contextual, object memory or olfactory memory, or do they participate in the different types of operations of explicit memory initial consolidation and storage, retrieval. There are two specific aims. For the first aim, the investigators will determine to what degree the different areas of the medial temporal lobe system contribute preferentially to one or another type of explicit memory tasks: spatial, contextual, object recognition, or olfactory. For a second specific aim, the investigators will determine whether memory retrieval can be disassociated from initial storage. If this is possible, they will attempt to identify the molecular nature of retrieval. They will attempt to determine whether different regions of the hippocampus are specialized for different memory operations such as consolidation and retrieval.